The present invention is related to a web-fed rotary printing press. In particular, the invention is related to movable folders and a former board arrangement for folding a plurality of printed ribbons in a web-fed rotary printing press.
In the production of newspapers, a plurality of paper webs is usually fed through an associated number of printing units to be printed on either one side or on both sides with a desired single or multi-color image. The printed webs are afterwards longitudinally cut into ribbons which are fed to a former board section including one or more former boards for applying a longitudinal fold to the ribbons. Before passing over the former boards, the ribbons are usually superposed by means of guide rollers before entering the former section and after exiting the former section, in order to obtain a desired paging and desired sectioning of the final newspaper.
After exiting the former board section, the superposed and longitudinally folded ribbons are then again superposed and fed to a downstream folder, in which the longitudinally folded superposed ribbons are cut and then folded crosswise into single signatures which are transported to a mailroom section, in which the final newspapers are gathered, stacked and collated for further shipment.
From the prior art, it is known to use former board sections in which three pairs of former boards are arranged above each other and the superposed and longitudinally folded ribbons are fed to a subsequent folder which is fixedly installed in the press room. The feeding of the folded and superposed ribbons to the folder is achieved by means of a plurality of guide rollers which are located below each of the former boards and around which each of the longitudinally folded superposed ribbons is passed.
Due to the so-called radius effect, which is caused by the outer ribbon of a multi-layered ribbon passing over a diverting roller having a greater distance from the center of rotation of the roller compared with the inner ribbon of the multi-layered ribbon, there is a certain likeliness of the occurrence of wrinkles and other defects of the printed ribbons which directly affect the printed image and general appearance of the newspapers. Moreover, there is also the danger of gussets or even tears of the ribbons or the occurrence of tension variation or a ribbon weave which also detrimentally affect print quality. Another problem arising when passing a plurality of printed ribbons over a diverting roll is that there may occur a marking of the freshly printed ink or a misregistration in the so-called cut-off register which actually defines the position at which the ribbons are cut crosswise in the folder section, in order to obtain a properly cut newspaper.
The main performance parameters which influence the probability of an occurrence of the above-described print affects are the paging of the newspapers, the diameter of the guide rollers, the angle of wrap of the ribbons around the guide rollers, the length of the section leads, the number of the gathered sections and the gains of the nip rollers for pulling the ribbons over the former boards, which are located below each of the former boards and the ability of the nip rollers to hold the papers.
One of the main problems which arises during the operation of the printing press is that severe wrinkles which are likely to fold over or tear, do not only produce visible print affects, but may also result in folder jams which inevitably lead to a shut-down of the printing press for a longer period of time, and therefore to a loss in output.
U.S. Pat. No. 5,775,222 purports to disclose a rotary printing press which includes folders which are movable via a yoke. One of the folders may be used as a primary folder, with the other folder being available as a replacement. UK 1,490,675 purports to discribe a method of interchanging folders in a printing machine, comprising lowering a folder to be removed from its operating position, moving the folder to be removed generally horizontally so as to remove it from the lowered position, moving the folder to be installed generally horizontally to be lowered position, and raising the folder to the installed to its operating position.
Having outlined the state of the art and its attendant disadvantages, it is an object of the present invention to provide for a folder arrangement in a web-fed rotary newspaper printing press, which reduces the risk of the occurrence of severe wrinkles in the images of the printed ribbons.
In accordance with a first embodiment of the present invention, a former board arrangement in a web-fed rotary newspaper printing press comprises a first and a second row of former boards, each row including a first, a second and a third former board for longitudinally folding one or more ribbons passing over the former boards. The first row of former boards is arranged preferably obliquely above the second row of former boards, and a movable folder to which the longitudinally folded webs are fed after exiting the former boards of the first and second row of former boards, is located below one of the former boards.
The combination of two rows of three former boards and a movable folder which may be located below any of the three former boards of the second row of former boards, reduces the likeliness of the occurrence of printed defects such as wrinkles and gussets, tares, tension variations, ribbons weave and marking, significantly.
Moreover, it was found that the variations in the print-to-cut register of the printed signatures in the subsequent folder section are also reduced by the former board arrangement according to the present invention.
According to another aspect of the present invention, a plurality of guide rollers or gathering rollers is provided preferably below each former board, in order to divert the longitudinally folded ribbons exiting the former boards to the movable folder, whereby all of the folded ribbons are preferably superposed by means of the guide rollers before entering the folder.
According to another aspect of the present invention, a plurality of superposed ribbons is passing over each of the former boards of the first and second rows of former boards, whereby the total number of superposed ribbons running over the former boards of the second row of former boards is preferably larger than the number of ribbons passing over the former boards of the first row of former boards.
The advantage which can be obtained by using a different number of superposed ribbons running over each of the former boards lies in the increase in the variety of different sections and the paging of the newspaper, as four ribbons or half-webs usually make up one section of the newspaper. By varying the number of ribbons passing over each former board, a desired arrangement of the sections in the newspaper can be obtained with a much higher flexibility. In this respect, it has also been found that it is advantageous if the total number of superposed ribbons passing over the former boards of the second row of former boards is larger than the number of ribbons passing over the first row of former boards, as the severity of the wrinkles and gussets and therefore the probability of print defects is being reduced.
According to another aspect of the present invention, a different number of superposed ribbons is passing over at least two of the former boards of the first row of former boards or of the second row of former boards, whereby in case of the first row of former boards, two superposed ribbons may pass over two of the former boards of the first row of former boards. In this embodiment, the former board having the largest number of ribbons is preferably located on the very outside of the first row of former boards.
In particular, it has shown to be advantageous if two superposed ribbons are passing over two of the former boards of the first row of former boards, and four superposed ribbons are passing over the remaining former board of the first row of former boards. A further reduction of the severity of wrinkles and gussets may be obtained if the two former boards which are folding two of the superposed ribbons each, are located side-by side and the remaining former board folding four superposed ribbons simultaneously is located at the very outside of the first row of former boards.
According to another aspect of the present invention, a different number of superposed ribbons is passing over at least two of the former boards of the second row of former boards. In this embodiment of the invention, the folding apparatus is preferably located below the former board of the second row of former boards which folds the largest number of superposed ribbons, so that these ribbons are directly fed into the folder without running over guide rollers before entering the folder.
In accordance with another embodiment of the present invention, a movable folder is employed, which significantly simplifies the process of changing the path of the folded ribbons, by allowing the folder to easily move below the former board folding the largest number of ribbons.
According to another embodiment of the present invention, preferably four superposed ribbons are passing over two of the former boards of the second row of former boards, and eight superposed ribbons are passing over the remaining former board of the second row of former boards. In this embodiment, the two former boards for folding four superposed ribbons each are preferably located side by side, and the former board folding eight superposed ribbons is accordingly located at the very outside of the second row of-former boards, preferably directly above the movable folder.
According to another embodiment of the present invention, the former boards of the first row of former boards are located substantially inline with the former boards of the second row of former boards, so that e. g. the tips of the former boards of each row are arranged in substantially vertical planes running through the former boards.
According to another embodiment of the present invention, the former boards of the first and second row of former boards may also be located offset to each other, preferably such that the tips of the former boards of the first row of former boards are located in substantially vertical planes which run between two adjacent former boards of the second row of former boards. By means of this tagged arrangement, the number of guide rollers for directing the superposed ribbons exiting the former boards of the first row of former boards, and therefore the likeliness for the occurrence of wrinkles and gussets can be further reduced.
In accordance with another embodiment of the present invention, a movable folder assembly includes a folder slidingly supported on a pair of rails and an actuator for moving the folder on said pair of rails.
The actuator preferably includes a hydraulic cylinder and a control unit for controlling said hydraulic cylinder. Preferably, the cylinder rod of the hydraulic cylinder is rigidly fixed to the platform and the body of the hydraulic cylinder is secured to the folder. Moreover, the hydraulic cylinder is preferably configured so that the cylinder body is the movable piece. In a preferred embodiment, this is accomplished by forming a bore through the length of the cylinder rod, and attaching the hose to the end of the rod. In this manner the hoses remain stationary as the folder is moved. This simplifies the layout of hydraulic hoses as compared with conventional hydraulic cylinder arrangements in which the hydraulic hoses move back and forth as the cylinder moves.
The movable folder assembly may be employed in combination with the former board arrangement described above, or may be used with conventional former board arrangements. The use of a movable folder significantly reduces a time required to re-web the folder in the event of a folder failure because, by moving a replacement folder into the same position as the original folder, there is no need to reallign the webs to compensate for a change in folder position. In addition, when used in conjunction with the former board arrangements described above, the use of movable folders significantly simplifies the process of changing the path of the folded ribbons, by allowing the folder to easily move below the former board folding the largest number of ribbons.
In accordance with a further aspect of this embodiment, the folder is supported on said rails by bearings. Preferably, the bearings are linear bearings, and most preferably, the folder is supported on at least one of said rails by dual-type linear bearings. The use of linear bearings provides a number of advantages including improved load distribution, and a reduced susceptabilty to failure due to contaminants (e.g. dirt) in or on the bearings and/or rails.
The folder assembly may also include a preset device for providing a plurality of preset folders positions along the rails. Preferably, the preset device is an absolute encoder.
In accordance with a still further aspect of this embodiment of the present invention, the movable folder includes a first folder and a second folder slidingly supported on the pair of rails. In one embodiment, the first folder is secured to the second folder so that the first and second folders move together along the rails. In an alternative embodiment, the first and second folders move separately along the rails.